PubMed · 14852615
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V FOGHT-NIELSEN. 1951. [Divinyl ether].. https://pubmed.ncbi.nlm.nih.gov/14852615/
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General anesthetics have been a mainstay of surgical practice for more than 150 years, but the mechanisms by which they mediate their important clinical actions remain unclear. Ion channels represent important anesthetic targets, and, although GABA(A) receptors have emerged as major contributors to sedative, immobilizing, and hypnotic effects of intravenous anesthetics, a role for those receptors is less certain in the case of inhalational anesthetics. The neuronal hyperpolarization-activated pacemaker current (Ih) is essential for oscillatory and integrative properties in numerous cell types. Here, we show that clinically relevant concentrations of inhalational anesthetics modulate neuronal Ih and the corresponding HCN channels in a subunit-specific and cAMP-dependent manner. Anesthetic inhibition of Ih involves a hyperpolarizing shift in voltage dependence of activation and a decrease in maximal current amplitude; these effects can be ascribed to HCN1 and HCN2 subunits, respectively, and both actions are recapitulated in heteromeric HCN1-HCN2 channels. Mutagenesis and simulations suggest that apparently distinct actions of anesthetics on V(1/2) and amplitude represent different manifestations of a single underlying mechanism (i.e., stabilization of channel closed state), with the predominant action determined by basal inhibition imposed by individual subunit C-terminal domains and relieved by cAMP. These data reveal a molecular basis for multiple actions of anesthetics on neuronal HCN channels, highlight the importance of proximal C terminus in modulation of HCN channel gating by diverse agents, and advance neuronal pacemaker channels as potentially relevant targets for clinical actions of inhaled anesthetics.
BACKGROUND: Anaesthetic preconditioning (A_PreC) and postconditioning (A_PostC) both provide protection against ischaemia-reperfusion in the heart. However, post-ischaemic gene responses may differ between the two therapeutic strategies. METHODS: Isolated perfused rat hearts were exposed to 40 min test ischaemia followed by 3 h reperfusion and used to determine transcriptional changes in response to A_PreC and A_PostC. A_PreC was induced by 15 min of isoflurane 2.1 vol% followed by 10 min of washout, and A_PostC was induced by 15 min of isoflurane 2.1 vol% administered at the onset of reperfusion. Untreated hearts served as ischaemic control (ISCH). Coupled-two way clustering (CTWC) and principal component analysis (PCA) were used to identify gene expression patterns. RESULTS: A_PreC (7[sd 1]%) and A_PostC (6[2]%) produced a similar decrease in infarct size (ISCH 36[1]%, P<0.05). However, post-ischaemic genomic reprogramming was completely different. Few genes were jointly regulated (2.1 per thousand of upregulated genes and 1.3% of downregulated genes). Eight stable gene clusters including three subclusters emerged from CTWC and were related to inflammation, signalling, ion channels, transcription factors, long interspersed repetitive DNA, heat shock response and remodelling. Two stable sample clusters were identified for postconditioned hearts (first cluster) and for all other protocols (second cluster), emphasizing the unique cardiac phenotype elicited by A_PostC. PCA revealed a close genomic relationship between A_PreC and non-ischaemic healthy myocardium. CONCLUSIONS: A_PreC, but not A_PostC, induces a post-ischaemic gene expression profile similar to virgin myocardium and prevents activation of the deleterious cardiac remodelling programme. Hence A_PreC and A_PostC are not interchangeable with respect to their molecular outcome in the heart.
Thermal unfolding of bovine serum albumin (BSA) has been studied in the presence of 2,2,2-trifluoroethanol (TFE) using high-sensitivity microdifferential scanning calorimetry. Quantitative thermodynamic parameters accompanying the thermal transitions have been evaluated. TFE is observed to be a stabilizer or a destabilizer of the folded state of BSA depending on the pH. CD spectroscopy revealed an increase in the alpha-helical content of BSA and a decrease in the tertiary structure in the presence of increasing molalities of TFE. Isothermal titration calorimetric results do not indicate appreciable binding of the TFE molecules to BSA. TFE quenches the steady-state tryptophan fluorescence of BSA only at higher molalities and there is no effect on the tryptophan fluorescence at lower molalities. The calorimetric and spectroscopic results obtained in this work suggest that solvent-mediated effects dominate the interaction of TFE with BSA and the binding component may be very weak. Since the binding component is very weak, one of the possibilities of anesthetic action of TFE molecules on the actual targets may be through perturbation of the structural and dynamic properties of the lipid bilayer so that the function of crucial but unspecified membrane proteins is affected.